1. Technical Field
This invention relates to a reciprocating plastic extruder and more particularly this invention relates to a miniature automatic shutoff nozzle tip for controlling flow of molten plastic fluid through a discharge chamber passageway and into a mold.
2. Description of Prior Art
The manufacturing process of injection molding is a primary form of manufacturing of plastic products in the world today. The demands of high molded part tolerances, dimensional stability, and shot-to-shot repeatability are increasing and better controls and mechanical components of the injection machines are required to meet the increasing demands. A major component that contributes to this process of improvement is the plasticating unit and specifically, the nozzle which is one of the components of the unit. The nozzle can be a one piece construction design or a two piece construction design where there is a nozzle body and “replaceable nozzle tip” that has a means for attachment, which is usually a thread. The miniature automatic shutoff nozzle tip of this invention is a component of the two piece design and is referred to as a “replaceable tip”. The two piece design nozzle has the advantage that it can be changed readily to match the radius, orifice and geometry of the internal passageway to match the specific resin being processed and the nozzle tip is much shorter than the one piece nozzle body and of course it is much easier to machine the internal geometry of a removable nozzle tip than it is to machine a standard length one piece nozzle. A properly designed nozzle will lead to fewer imperfections of the molded parts. Imperfect molded parts cost the industry billions of dollars per year. An improvement in the nozzle is desirable to eliminate imperfect molded parts.